SQL NOT NULL Constraint

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The NOT NULL constraint ensures that a column must contain a value and cannot store NULL (empty) values.

In simple terms:
If a column is defined as NOT NULL, every record must have a value for that column.
This is used for mandatory fields in a table.

Why NOT NULL is Important
   • Ensures data integrity
   • Prevents missing important data
   • Enforces mandatory fields

Example: Orders Table

When creating an Orders table, some columns must always have data such as OrderID, CustomerID, and OrderDate.

Create Table Example
CREATE TABLE Orders (
    OrderID INT NOT NULL,
    CustomerID INT NOT NULL,
    OrderDate DATE NOT NULL,
    Amount DECIMAL(10,2),
    Status VARCHAR(50)
);

Simple Definition
The NOT NULL constraint ensures that a column cannot contain NULL values and must always have a value when inserting or updating records.

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